Editing wordpress

hi everybody 🙂

I need a little help about coding. at some sites there are website seo tests and when I tested my site there are many coding errors at the report. I know php coding but I cant find the files of my site at ftp to edit.! 🙁

my homepage is a specific page that I choose its name is home. I looked at ftp wp-content/themes/(mythemename)index.php and wp-content/themes/(mythemename)/home.php but there are other codes.

is my homepage mix of other php files? I didnt understand the wordpress coding :(((